This is the enhanced recordings of the Messenger series by Prof Feynman in 1964 at Cornell Microsoft's Bill Gates got ownership of this series for a research project called [Project Tuva](microsoft.com/en-us/research/project/tuva-richard-feynman/) from the Cornell University.
Project Tuva has been discontinued and the website not maintained. But the lectures are pure gold - I thought it should be accessible to you. Please note that the content is still owned by Microsoft and hence will play on their Azure Player.